This invention relates to the production of arylene sulfide polymers. In one aspect, this invention relates to the production of phenylene sulfide polymers. In another aspect, this invention relates to the production of arylene sulfide polymers having a high extrusion rate or a low inherent viscosity. In a further aspect, this invention relates to the production of poly(phenylene sulfide) having a high extrusion rate or a low inherent viscosity.
A basic process for the production of arylene sulfide polymers from polyhalo-substituted aromatic compounds by reaction with an alkali metal sulfide in the presence of a polar organic compound is disclosed in U.S. Pat. No. 3,354,129. This patent also discloses that the molecular weight of the arylene sulfide polymers can be reduced by the use of monohalo-substituted aromatic compounds as chain terminating agents or by the use of an excess of one of the reactants, such as p-dichlorobenzene, in the polymerization reaction mixture. The use of excess dihalo-substituted aromatic compound reactant suffers from the disadvantages of increased cost of added reactant materials, difficulty in polymer recovery, and the need for recovering and recycling excess dihalo-substituted aromatic reactant to the polymerization zone. In addition, previous attempts to employ monohalo-substituted aromatic compounds as chain terminating agents to obtain arylene sulfide polymers of reduced molecular weight have given generally unsatisfactory results because: (1) either the monohalo compound was so unreactive that it could not compete with the polyhalo-substituted aromatic compound monomer and thus had essentially no effect on the polymer produced in its presence, or (2) the monohalo compound, while activated relative to the polyhalo-substituted aromatic compound, possessed an activating group which was unstable under polymerization and/or polymer recovery conditions thus promoting polymer instability, or (3) the monohalo compound, while activated relative to the polyhalo-substituted aromatic compound, was relatively expensive compared to the polyhalo-substituted aromatic compound.
Arylene sulfide polymers can be characterized at least in part in terms of a melt flow rate. It is generally considered that a melt flow rate is inversely related molecular weight for polymeric materials in general and for arylene sulfide polymers in particular. Extrusion rate, which is more specifically defined hereinafter, is a specific type of melt flow rate which is particularly useful for characterizing arylene sulfide polymers in the lower molecular weight range. Arylene sulfide polymers can also be characterized at least in part in terms of inherent viscosity. It is generally considered that inherent viscosity, which is more specifically defined hereinafter, is directly related to molecular weight for polymeric materials in general and for arylene sulfide polymers in particular.
Arylene sulfide polymers having a relatively high extrusion rate or relatively low inherent viscosity are desirable for a variety of applications such as encapsulation of electronic components and coating formulations. For example, U.S. Pat. Nos. 4,337,182 and 4,482,665 provide exemplary disclosures of compositions comprising arylene sulfide polymers which are employed in the encapsulation of electronic components.